The invention relates to hard disc drives, and more specifically to the reduction of contamination within the housing of a hard disc drive.
Magnetic disc drives are used for storing information. In such a disc drive, a magnetic disc rotates at high speed, and a transducing head flies over a surface of the disc. This transducing head records information on the disc surface by impressing a magnetic field on the disc. Information is read back using the head by detecting magnetization of the disc. The transducing head is moved radially across the surface of the disc so that different data tracks can be read back.
Over the years, storage density has tended to increase and the size of the storage system has tended to decrease. This trend has led to greater precision and lower tolerance in the manufacture and operation of magnetic storage discs. For example, to achieve increased storage densities, the transducing head must be placed increasingly close to the surface of the storage disc. Further, each of the bits is packed more closely together on the disc surface. All of this means that any contamination within the disc drive can have a negative effect on the recording and reproducing capabilities of the disc drive. The contamination which can have a negative effect on the efficiency and data storage capability of the drive can be generated by any part of the drive including the spindle motor.
Material choice for the spindle motor is one of the critical factors in reducing risk of contamination for various reasons. It has been a common practice to make motor components from free machining steels, e.g. 430F, 303, etc., which contain free machining additives like sulfur, selenium, tellurium, etc. Most of these additives have much higher vapor pressure than other alloying elements found in steel and other alloys. As a result, these elements, especially sulfur, have a substantial tendency to outgas if they remain in the form of free sulfur. Such elements are susceptible to outgassing even in the form of manganese sulfide, which is the most common form of sulfur in an alloy of the type which is commonly used in a spindle motor. At elevated temperature and in the presence of moisture, manganese sulfide reacts to form hydrogen sulfide that causes severe damage to the drive components by having corrosive effect.
One of the common methods of reducing such outgassing is passivation. However, passivation brings new problems as most passivation processes include use of strong acids like nitric acid or sulfuric acid. The use of acids results in the formation of anions such as nitrate which themselves can cause contamination problems. Therefore, the need continues to exist for an effective method to reduce generation of contaminants by a spindle motor.
In summary, the present design is intended to reduce or eliminate contaminants thrown off by a spindle motor incorporated in a disc drive.
In a preferred form of the present invention, a non-reactive hard coating of carbon or ceramic is applied to the major components of the spindle motor which are exposed to the atmosphere internal to the hard disc drive. By having such a thin layer of carbon or other ceramic coating, it will protect against outgassing of motor components and create a neutral or non-reactive surface that does not promote corrosion. The coating thickness can be preferably in the order of nanometers to microns depending upon the drive design and the operating conditions.
Other features and advantages of this invention will be apparent to a person of skill in the art who studies the invention disclosure. Therefore, the scope of the invention will be better understood by reference to an example of an embodiment, given with respect to the following figures.